Our overall objective is to gain a molecular understanding of morphogenetic processes in higher organisms by examining the development of the embryonic limb. In this effort we are focussing on the process of chondrogenesis. We will continue to probe the regulatory events which take place in normal cells at the time of chondrogenesis and which fail to take place in nanomelic cartilage. We will also determine if there are any similarities or dissimilarities between the various PGS fractions of the various tumors we have examined. BIBLIOGRAPHIC REFERENCES: Goetinck, P.F. and Pennypacker, J.P. (1977). Controls in the acquisition and maintenance of chondrogenic expression. In Vertebrate Limb and Somite Morphogenesis (ed. D.A. Ede, J.R. Hinchliffe, & M. Balls). Cambridge University Press. In press. Royal, P.D. and Goetinck, P.F. (1977). In vitro chondrogenesis in mouse limb bud mesenchymal cells; changes in ultrastructure and proteoglycan synthesis. J. Embryol. Exptl. Morph. In press.